640441649 has 4 divisors (see below), whose sum is σ = 641069940. Its totient is φ = 639813360.

The previous prime is 640441643. The next prime is 640441661. The reversal of 640441649 is 946144046.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 357966400 + 282475249 = 18920^2 + 16807^2 .

It is a cyclic number.

It is not a de Polignac number, because 640441649 - 2⁸ = 640441393 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640441643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 312614 + ... + 314655.

It is an arithmetic number, because the mean of its divisors is an integer number (160267485).

Almost surely, 2^640441649 is an apocalyptic number.

It is an amenable number.

640441649 is a deficient number, since it is larger than the sum of its proper divisors (628291).

640441649 is a wasteful number, since it uses less digits than its factorization.

640441649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 628290.

The product of its (nonzero) digits is 82944, while the sum is 38.

The square root of 640441649 is about 25306.9486307615. The cubic root of 640441649 is about 861.9720604169.

The spelling of 640441649 in words is "six hundred forty million, four hundred forty-one thousand, six hundred forty-nine".